1. Field
The presently disclosed subject matter relates to methods and systems for detecting a leak in a pipeline. More particularly, the presently disclosed subject matter relates to detecting a leak in a pipeline using a sensing cable including an optical fiber sensor array aligned with a heating element.
2. Description of Related Art
Components of certain equipment, such as that used in the petroleum and petrochemical industry, which includes the exploration, production, refining, manufacture, supply, transport, formulation or blending of petroleum, petrochemicals, or the direct compounds thereof, are often monitored to maintain reliable operation. However, such components can involve harsh conditions, such as high temperature, high pressure, and/or a corrosive environment, making it difficult or costly to obtain reliable measurements.
Energy and petroleum industry often requires use of pipelines located in underwater environments. There is a continued need to ensure such pipelines are free of significant leaks. For example, detecting leaks in a pipeline can increase efficiencies, and prevent or remediate spills and other undesirable conditions.
Conventional techniques for pipeline leak detection include computational pipeline monitoring (CPM), acoustic sensors, distributed fiber optic temperature or acoustic sensors. CPM is a wide-ranging term used to describe many computer-based leak detection systems. It uses pipeline flow and/or pressure measurements, governing models and alarm evaluation for leak detection and confirmation. The governing models can be based on mass balance, volume balance, pressure measurements, transient fluid flow models, and/or statistical analysis of historical pipeline events. CPM is the most commonly utilized and mature technology for pipeline leak detection and has been used in both onshore and offshore applications and the governing models have been tested extensively. The main limitations of CPM include lower sensitivity due to instrumentation performance and false positive alarms in transient pipeline conditions. Other pipeline leak detection techniques that are mainly used for pipeline leak location involve acoustic sensors. Acoustic leak detection involves sensing the pressure wave or sound generated by a leak. This is an external type of system and is typically used for periodic inspection or determining leak location after a leak alarm has been generated by a method such as CPM. These sensors can be hand held or mounted on a vehicle. The pressure difference created by the leak is the most important parameter in detection. The instrumentation signals are filtered using advanced signal processing software. The signal is characteristic of leak flow rate, pressure drop, type of fluid. Other relatively new leak detection techniques involve the use of distributed fiber optic sensors. This is external type of leak detection system. Pulses of laser light are sent into a FO cable laid along the length of the pipeline. The light is partially backscattered by the cable material throughout the cable length generating scattered components. This backscattering process is influenced by the cable physical properties, which are in turn dependent on the ambient temperature changes and acoustic vibrations that may be caused by pipeline leaks. Therefore, by analyzing the characteristics of the backscattered light, information, i.e. ambient temperature or acoustic vibrations, associated with the pipeline leaks along the cable may be obtained. The sensitivity of commercially available fiber optic temperature or acoustic sensor cables needs to be verified for pipeline leak detection.
However, there is a continued need for improved techniques for detecting leaks in a pipeline.